The quenching of minijets (particles with $p_T\gg T,{\Lambda }_{\mathrm{QCD}}$) in ultrarelativistic heavy-ion collisions has been one of the main predictions and discoveries at the BNL Relativistic Heavy Ion Collider. We analyze the correlation between different observables like the nuclear modification factor $R_{\mathit{AA}}(p_T)$, the elliptic flow, and the ratio of quark to gluon suppressions. We show that the temperature (or entropy density) dependence of the in-medium energy loss strongly affects the relation among these observables. In particular, the large elliptic flow and the nearly equal $R_{\mathit{AA}}(p_T)$ of quarks and gluons can be accounted for only if the energy loss occurs mainly around $T_c$ and the $q\leftrightarrow g$ conversion is significant. The use of an equation of state fitted to lattice QCD calculations, slowing down the cooling as $T\to T_c$, seems to contribute to both the enhancement of $v_2$ and the efficiency of the conversion mechanism.

The nuclei ${}^{230}\mathrm{U}$ and ${}^{232}\mathrm{U}$ were populated in the compound nucleus reactions ${}^{232}\mathrm{Th}$($\alpha ,6n$) and ${}^{232}\mathrm{Th}$($\alpha ,4n$), respectively. Gamma rays from these nuclei were observed in coincidence with a recoil detector. A comprehensive set of in-band $E2$ transitions were observed in the lowest lying negative-parity band of ${}^{232}\mathrm{U}$ while one $E2$ transition was also observed for ${}^{230}\mathrm{U}$. These allowed $B(E1;I^{-}\to I^{+}-1)/B(E2;I^{-}\to I^{-}-2)$ ratios to be extracted and compared with systematics. The values are similar to those of their Th and Ra isotones. The possibility of a tetrahedral shape for the negative-parity U bands appears difficult to reconcile with the measured $Q_2$ values for the isotone ${}^{226}\mathrm{Ra}$.

Helicity-dependent incoherent pion photoproduction in the reaction $\mathrm{\gamma ⃗}\mathrm{d⃗}\to \pi \mathit{NN}$ is studied in the framework of the diagrammatic approach. Contributions to the reaction amplitude from diagrams corresponding to impulse approximation as well as $\mathit{NN}$ and $\pi N$ interactions in the final state have been evaluated. The elementary $\gamma N\to \pi N$ operator is taken from the MAID and SAID models. A detailed comparison of the predictions with recent experimental data by the GDH and A2 collaborations at energies below 500 MeV is presented. Reasonable agreement with the data on the yields and cross sections for the polarized beam and polarized target has been achieved in all channels. The unpolarized data of the GDH and A2 collaborations have also been analyzed within the approach. A strong overestimation for the neutral channel has been found. At the same time, the model provides a quite satisfactory description of the unpolarized data for the charged channels. The sensitivity of the obtained results to the choice of the elementary $\gamma N\to \pi N$ operator is discussed in detail. The contribution of the $\gamma d\to \pi \mathit{NN}$ reaction to the GDH sum rule for the deuteron up to a photon energy of 1.65 GeV has been evaluated with the result of $235\pm 25$ $\mu$b.

The systematics of one-quasiparticle configurations in neutron-rich Sr, Zr, and Mo odd isotopes is studied within the Hartree-Fock-Bogoliubov plus equal filling approximation method preserving both axial and time-reversal symmetries. Calculations based on the Gogny energy density functional with both the standard D1S parametrization and the new D1M incarnation of this functional are included in our analysis. The nuclear deformation and shape coexistence inherent to this mass region are shown to play a relevant role in the understanding of the spectroscopic features of the ground and low-lying one-quasineutron states.

A $98\%$ pure ${}^{242\mathrm{m}}$Am ($K=5^{-}$, $t_{1/2}=141$ years) isomeric target was Coulomb excited with a $170.5$-MeV ${}^{40}\mathrm{Ar}$ beam. The selectivity of Coulomb excitation, coupled with the sensitivity of Gammasphere plus CHICO, was sufficient to identify $46$ new states up to spin $18\hslash$ in at least four rotational bands; $11$ of these new states lie in the isomer band, $13$ in a previously unknown yrast $K^{\pi }=6^{-}$ rotational band, and $13$ in a band tentatively identified as the predicted yrast $K^{\pi }=5^{+}$ band. The rotational bands based on the $K^{\pi }=5^{-}$ isomer and the $6^{-}$ bandhead were populated by Coulomb excitation with unexpectedly equal cross sections. The $\gamma$-ray yields are reproduced by Coulomb excitation calculations using a two-particle plus rotor model (PRM), implying nearly complete $\Delta K=1$ mixing of the two almost-degenerate rotational bands, but recovering the Alaga rule for the unperturbed states. The degeneracy of the $5^{-}$ and $6^{-}$ bands allows for precise determination of the mixing interaction strength $V$, which approaches the strong-mixing limit; this agrees with the $50\%$ attenuation of the Coriolis matrix element assumed in the model calculations. The fractional admixture of the $I_K^{\pi }=6_6^{-}$ state in the nominal $6_5^{-}$ isomer band state is measured within the PRM as $45.6_{-1.1}^{+0.3}\%$. The $E$2 and $M$$1$ strengths coupling the $5^{-}$ and $6^{-}$ bands are enhanced significantly by the mixing, while $E1$ and $E2$ couplings to other low-$K$ bands are not measurably enhanced. The yields of the $5^{+}$ band are reproduced by an $E3$ strength of $\approx$15 W.u., competitive with the interband $E2$ strength. Alignments of the identified two-particle Nilsson states in ${}^{242}\mathrm{Am}$ are compared with the single-particle alignments in ${}^{241}\mathrm{Am}$.

We have measured the half-life of the ${\beta }^{-}$ decay of ${}^{198}\mathrm{Au}$ to be $2.6948(9)$ d, with the nuclide sited in an insulating environment. Comparing this result with the half-life we measured previously with a metallic environment, we find the half-lives in both environments to be the same within $0.04\%$, thus contradicting a prediction that screening from a “plasma” of quasifree electrons in a metal increases the half-life by as much as $7\%$.

Final-state-exclusive momentum distributions of fast, forward-traveling residual nuclei, following two-nucleon removal from fast secondary radioactive beams of projectile nuclei, can and have now been measured. Assuming that the most important reaction mechanism is the sudden direct removal of a pair of nucleons from a set of relatively simple, active shell-model orbital configurations, such distributions were predicted to depend strongly on the total angular momentum $I$ carried by the two nucleons—the final-state spin for spin $0^{+}$ projectiles. The sensitivity of these now-accessible observables to specific details of the (correlated) two-nucleon wave functions is of importance. We clarify that it is the total orbital angular momentum $L$ of the two nucleons that is the primary factor in determining the shapes and widths of the calculated momentum distributions. It follows that, with accurate measurements, this dependence upon the $L$ makeup of the two-nucleon wave functions could be used to assess the accuracy of (shell- or many-body-) model predictions of these two-nucleon configurations. By using several tailored examples, with specific combinations of active two-nucleon orbitals, we demonstrate that more-subtle structure aspects may be observed, allowing such reactions to probe and/or confirm the details of theoretical model wave functions.

Differential cross sections for elastic-scattering and neutron-transfer reactions along with cross sections for fusion in the ${}^8\mathrm{He}$$+$${}^{65}\mathrm{Cu}$ system are reported at energies above the Coulomb barrier ($E_{\mathrm{lab}}=$ $19.9$ and $30.6$ MeV). The present work demonstrates the feasibility of using inclusive measurements of characteristic in-beam $\gamma$ rays with low-intensity ($~$$10$${}^5$ pps) radioactive ion beams to obtain the residue cross sections for fusion and neutron transfer. Exclusive measurements of $\gamma$ rays in coincidence with light charged particles have been used to further characterize the direct reactions induced by this double-Borromean nucleus. Coupled reaction channels calculations are used to illustrate the important role played by the transfer channels and to help in understanding the influence of the structure of ${}^8\mathrm{He}$ on the reaction mechanism.

The production and space-time evolution of charm and bottom quarks in nucleus-nucleus collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) are investigated with the partonic transport model BAMPS (Boltzmann approach of multiparton scatterings). Heavy quarks, produced in primary hard parton scatterings during nucleon-nucleon collisions, are sampled using the Monte Carlo event generator pythia or the leading-order minijet model in conjunction with the Glauber model, revealing a strong sensitivity on the parton distribution functions, scales, and heavy-quark mass. In a comprehensive study exploring different charm masses, $K$ factors, and possible initial gluon conditions, secondary production and the evolution of heavy quarks are examined within a fully dynamic BAMPS simulation for central heavy-ion collisions at RHIC and LHC. Although charm production in the quark-gluon plasma can be neglected at RHIC, it is significant at LHC but very sensitive to the initial conditions and the charm mass. Bottom production in the quark-gluon plasma, however, is negligible both at RHIC and LHC.

We present the transverse momentum spectra and rapidity distributions of ${\pi }^{-}$ and ${\mathrm{K}}_S^0$ in Ar $+$ KCl reactions at a beam kinetic energy of $1.756$ $A$ GeV measured with the High Acceptance Di-Electron Spectrometer (HADES). The reconstructed ${\mathrm{K}}_S^0$ sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental ${\pi }^{-}$ and ${\mathrm{K}}_S^0$ distributions to predictions by the Isospin Quantum Molecular Dynamics (IQMD) model. The model calculations show that ${\mathrm{K}}_S^0$ at low transverse momenta constitute a particularly well-suited tool to investigate the kaon in-medium potential. Our ${\mathrm{K}}_S^0$ data suggest a strong repulsive in-medium ${\mathrm{K}}^0$ potential of about 40 MeV strength.

We compute the spectral densities of $T^{\mu \nu }$ and $J^{\mu }$ in high-temperature QCD plasmas at small frequency and momentum, $\omega ,k~g^{4}T$. The leading log Boltzmann equation is reformulated as a Fokker-Planck equation with nontrivial boundary conditions, and the resulting partial differential equation is solved numerically in momentum space. The spectral densities of the current, shear, sound, and bulk channels exhibit a smooth transition from free-streaming quasiparticles to ideal hydrodynamics. This transition is analyzed with conformal and nonconformal second-order hydrodynamics and a second-order diffusion equation. We determine all of the second-order transport coefficients that characterize the linear response in the hydrodynamic regime.

We study the properties of ${\mathrm{K̄}}^{*}$ mesons in nuclear matter using a unitary approach in coupled channels within the framework of the local hidden gauge formalism and incorporating the $\mathrm{K̄}\pi$ decay channel in matter. The in-medium ${\mathrm{K̄}}^{*}N$ interaction accounts for Pauli blocking effects and incorporates the ${\mathrm{K̄}}^{*}$ self-energy in a self-consistent manner. We also obtain the ${\mathrm{K̄}}^{*}$ (off-shell) spectral function and analyze its behavior at finite density and momentum. At a normal nuclear matter density, the ${\mathrm{K̄}}^{*}$ meson feels a moderately attractive potential, while the ${\mathrm{K̄}}^{*}$ width becomes five times larger than in free space. We estimate the transparency ratio of the $\gamma A\to K^{+}{K}^{*-}{A}^{\prime }$ reaction, which we propose as a feasible scenario at the present facilities to detect changes in the properties of the ${\mathrm{K̄}}^{*}$ meson in nuclear medium.

The roles played by mesons in the electromagnetic form factors of the nucleon are explored using as a basis a model containing vector mesons with coupling to the continuum together with the asymptotic $Q^2$ behavior of perturbative QCD. Specifically, the vector dominance model (GKex) developed by E. L. Lomon is employed, as it is known to be very successful in representing the existing high-quality data published to date. An analysis is made of the experimental uncertainties present when the differences between the GKex model and the data are expanded in orthonormal basis functions. A main motivation for the present study is to provide insight into how the various ingredients in this model yield the measured behavior, including discussions of when dipole form factors are to be expected or not, of which mesons are the major contributors, for instance, at low $Q^2$ or large distances, and of what effects are predicted from coupling to the continuum. Such insights are first discussed in momentum space, followed by an analysis of how different and potentially useful information emerges when both the experimental and theoretical electric form factors are Fourier transformed to coordinate space. While these Fourier transforms should not be interpreted as “charge distributions,” nevertheless the roles played by the various mesons, especially those which are dominant at large or small distance scales, can be explored via such experiment–theory comparisons.

Self-consistent mean-field methods based on phenomenological Skyrme effective interactions are known to exhibit spurious spin and spin-isospin instabilities both at zero and finite temperatures when applied to homogeneous nuclear matter at the densities encountered in neutron stars and in supernova cores. The origin of these instabilities is revisited in the framework of the nuclear energy density functional theory, and a simple prescription is proposed to remove them. The stability of several Skyrme parametrizations is reexamined.

The cross section for the reaction $p+{}^6\text{Li}\to \eta +{}^7\text{Be}$ was measured at an excess energy of $11.28$ MeV above threshold by detecting the recoiling ${}^7\mathrm{Be}$ nuclei. A dedicated set of focal plane detectors was built for the magnetic spectrograph Big Karl and was used for identification and four-momentum measurement of ${}^7\mathrm{Be}$. A differential cross section of $\frac{d\sigma }{d\Omega }=[0.69\pm 0.20\text{(stat.)}\pm 0.20\text{(syst.)}]\hspace{0.5em}\text{nb/sr}$ for the ground state plus $1/2^{-}$ was measured. The result is compared to model calculations.

The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of ${}^{238}\mathrm{U}$ projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify $40$ new heavy neutron-rich nuclei: ${}^{205}\mathrm{Pt}$, ${}^{207-210}\mathrm{Au}$, ${}^{211-216}\mathrm{Hg}$, ${}^{214-217}\mathrm{Tl}$, ${}^{215-220}\mathrm{Pb}$, ${}^{219-224}\mathrm{Bi}$, ${}^{223-227}\mathrm{Po}$, ${}^{225-229}\mathrm{At}$, ${}^{230,231}\mathrm{Rn}$, and ${}^{233}\mathrm{Fr}$. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

Within the framework of the improved isospin-dependent quantum molecular dynamics model, the dynamics of pion emission in heavy-ion collisions in the region of $1$$A$ GeV energies as a probe of nuclear symmetry energy at suprasaturation densities is investigated systematically. The total pion multiplicities and the ${\pi }^{-}/{\pi }^{+}$ yields are calculated for selected Skyrme parameters SkP, SLy6, Ska, and SIII and also for the cases of different stiffness of symmetry energy with the parameter SLy6. The influence of Coulomb potential, symmetry energy, and in-medium pion potential on the pion production is investigated and compared to each other by analyzing the distributions of transverse momentum and longitudinal rapidity and also the excitation functions of the total pion and the ${\pi }^{-}/{\pi }^{+}$ ratio. The directed flow, elliptic flow, and polar-angle distributions are calculated for the cases of different collision centralities and also the various stiffnesses of the symmetry energies. A comparison of the calculations with the available experimental data is performed.

We show that the classical and strongly coupled quark-gluon plasma is characterized by a multiple of structure factors that obey generalized Orstein-Zernicke equations. We use the canonical partition function and its associated density functional to derive analytical equations for the density and charge monopole structure factors for arbitrary values of $\Gamma =V/K$, the ratio of the mean potential to the Coulomb energy. The results are compared with SU(2) molecular dynamics simulations.

Measurements of the double-differential proton production cross-section $d^2\sigma /dpd\Omega$ in the range of momentum $0.5\hspace{0.5em}\mathrm{GeV}/c⩽p<8.0\hspace{0.5em}\mathrm{GeV}/c$ and angle $0.05\hspace{0.5em}\text{rad}⩽\theta <0.25\hspace{0.5em}\text{rad}$ in collisions of charged pions and protons on beryllium, carbon, aluminium, copper, tin, tantalum, and lead are presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN Proton Synchrotron. Incident particles were identified by an elaborate system of beam detectors and impinged on a target of $5\%$ of a nuclear interaction length. The tracking and identification of the produced particles was performed using the forward spectrometer of the HARP experiment. Results are obtained for the double-differential cross-sections mainly at four incident beam momenta ($3,5,8$, and $12$ $\text{GeV}/c$). Measurements are compared with predictions of the geant4 and mars Monte Carlo generators.

The -beam asymmetry $\Sigma$ in the photoproduction of negative pions on quasi-free neutrons in a deuterium target was measured at the Grenoble Anneau Accelerateur Laser in the energy interval $700-1500$ MeV and over a wide angular range, using polarized and tagged photons. Results are compared with recent partial-wave analyses.